1. Field of the Invention
The present invention relates to marine propulsion systems. More specifically, the present invention relates to a marine propulsion system including an engine.
2. Description of the Related Art
Conventionally, marine propulsion units (marine propulsion system) including an engine are known in the art (for example, see JP-A-Hei 9-263294). JP-A-Hei 9-263294 discloses a marine propulsion unit including an engine and a power transmission mechanism transmitting a driving force of the engine to a propeller in a certain fixed reduction ratio. The marine propulsion unit is arranged in a manner such that the driving force of the engine is transmitted directly to the propeller through the power transmission mechanism such that the rotational speed of the propeller increases in proportion to the engine speed as the engine speed increases.
However, the marine propulsion unit (marine propulsion system) disclosed in JP-A-Hei 9-263294 has a problem in that it is difficult to improve acceleration performance at low speed when speed reduction ratios of the power transmission mechanism are set to gain a larger maximum speed. Conversely, this causes a problem in that it is difficult to gain a larger maximum speed when the speed reduction ratios of the power transmission mechanism are set to improve the acceleration performance at low speed. In other words, the marine propulsion unit disclosed in JP-A-Hei 9-263294 has a problem in that it is difficult for an operator of a boat to achieve both acceleration performance and maximum speed at levels that he/she desires.